Fixed comparing Date and DateTime64

src/Functions/FunctionsComparison.h

@@ -1216,7 +1216,10 @@ public:
         {
             return res;
         }
-        else if (isColumnedAsDecimal(left_type) || isColumnedAsDecimal(right_type))
+        else if ((isColumnedAsDecimal(left_type) || isColumnedAsDecimal(right_type))
+                 // Comparing Date and DateTime64 requires implicit conversion,
+                 // otherwise Date is treated as number.
+                 && !(date_and_datetime && (isDate(left_type) || isDate(right_type))))
         {
             // compare
             if (!allowDecimalComparison(left_type, right_type) && !date_and_datetime)

tests/queries/0_stateless/01561_Date_and_DateTime64_comparision.reference

@@ -0,0 +1,3 @@
+-1	DateTime64(1, \'UTC\')	<	1	1	1	<=	1	1	1	=	0	0	0	>=	0	0	0	>	0	0	0	!=	1	1	1
+0	DateTime64(1, \'UTC\')	<	0	0	0	<=	0	1	0	=	0	1	0	>=	1	1	1	>	1	0	1	!=	1	0	1
+1	DateTime64(1, \'UTC\')	<	0	0	0	<=	0	0	0	=	0	0	0	>=	1	1	1	>	1	1	1	!=	1	1	1

tests/queries/0_stateless/01561_Date_and_DateTime64_comparision.sql

@@ -0,0 +1,43 @@
+SELECT
+    n,
+    toTypeName(dt64) AS dt64_typename,
+
+    '<',
+    dt64 < d,
+    toDate(dt64) < d,
+    dt64 < toDateTime64(d, 1, 'UTC'),
+    
+    '<=',
+    dt64 <= d,
+    toDate(dt64) <= d,
+    dt64 <= toDateTime64(d, 1, 'UTC'),
+
+    '=',
+    dt64 = d,
+    toDate(dt64) = d,
+    dt64 = toDateTime64(d, 1, 'UTC'),
+    
+    '>=',
+    dt64 >= d,
+    toDate(dt64) >= d,
+    dt64 >= toDateTime64(d, 1, 'UTC'),
+    
+    '>',
+    dt64 > d,
+    toDate(dt64) > d,
+    dt64 > toDateTime64(d, 1, 'UTC'),
+
+    '!=',
+    dt64 != d,
+    toDate(dt64) != d,
+    dt64 != toDateTime64(d, 1, 'UTC')
+FROM 
+(
+    SELECT
+        number - 1 as n,
+        toDateTime64(toStartOfInterval(now(), toIntervalSecond(1), 'UTC'), 1, 'UTC') AS dt64,
+        toDate(now(), 'UTC') - n as d
+    FROM system.numbers
+    LIMIT 3
+)
+FORMAT TabSeparated